In a system that uses an electrically erasable memory, with a precondition that data stored therein is rewritten, for a process that correlates logical information and physical information, physical information corresponding to all logical information is required. In addition, as another precondition, a process that correlates logical information and physical information using a redundant portion peculiar to such an electrically erasable memory is required. Moreover, since such an electrically erasable memory has a verify function that verifies written data by itself, it is not necessary to externally verify data.
Unlike with an electrically erasable memory, an irreversibly write memory of which data can be written one time is known. This memory is called a write once type memory or OTP (One Time Programmable ROM). Normally, an irreversibly write memory is non-volatile. In other words, once data is written to an irreversibly write memory, the data cannot be erased. Thus, after the power of an irreversibly write memory is turned off, data stored therein is retained.
When a data managing method for an electrically erasable memory is applied for the forgoing irreversibly write memory, the irreversibly write memory may not be effectively controlled. In addition, a correlation table for logical information and physical information results in a decrease of the memory capacity that the user can use.
It is therefore desirable to provide a data managing method that can be suitably and effectively applied to an irreversibly writeable memory.